The objectives of this research involve the syntheses and characterization of synthetic analogues of various heme proteins. The reactions of interest include 1) O2 binding by hemoglobin and leg-hemoglobin, 2) O2 activation and hydrocarbon hydroxylation by the monooxygenase cytochrome P-450, and 3) oxidant detoxification by catalase and peroxidase. We have discovered that O2 binding of 5-coordinate porphyrinatoiron(II) complexes shows cooperativity reminiscent of hemoglobin. Experiments are discussed which will delineate the molecular mechanisms which modulate the O2 affinities of such complexes and, by analogy, of heme proteins. Other studies will attempt to demonstrate the origin of the anomalously high O2 affinities of some non-mammalian heme proteins, notably leg-hemoglobin. We have produced catalytic hydrocarbon hydroxylation by porphyrinato iron(III) complexes using hydroperoxides which shows both similarities and differences to that shown by cytochrome P-450. Extensions of our present work are geared to the demonstration of NIH shift and the intermediacy of arene epoxides in such model systems. The effect of hydride donor reductants on stable iron-dioxygen complexes will also be investigated with the hope of mimicking monooxygenase activation of dioxygen. We have isolated a sterically encumbered porphyrin which should lead to synthetic analogues of the Compounds I and II of peroxidase, catalase and haloperoxidase. Because of its design this porphyrin, unlike others, should be quite resistant to oxidative degradation and ring cleavage. Experiments are planned to test this hypothesis and to isolate high oxidation state (Fe(IV) and FE(V)) intermediates from this macrocycle. Low temperature and flash photolytic solution and gas-solid state experiments are also described which may provide new insights into the structure and function of the hydroperoxidases.